ISI Insight – Making separate TETRA systems work together
Article courtesy of EADS, who have been awarded the world’s first TETRA ISI interoperability certificate
One of the original promises of the TETRA standard was to meet the Schengen requirements for public safety communication – especially across borders.
The goal of Schengen countries has been to allow free movement of people and goods. In practice, this has meant that the strict controls at the national borders have been substituted by signs at the roadside. People and companies have benefited, but authorities have recognised that they need better cooperation across borders in their fight against drug trafficking and organised crime.
Cooperation calls for better communications: authorities from the bordering countries need to work together, so their radio networks need to work together as well. TETRA including Inter-System Interface (ISI) is the standard that allows this.
The European Schengen requirements were not the only reason for developing the TETRA ISI. There is a clear need to be able to connect cross-border – not only for authority networks, but also regional, public and private radio networks.
From TETRA standard to interoperable ISI
The TETRA standard is defined by ETSI (European Telecommunication Standard Institute) with ISI being one part of this standard. The details how ISI shall be implemented and verified in interoperability tests were defined in TETRA Interoperability Profiles (TIP) by the TETRA Association in co-operation with ETSI.
TETRA Interoperability certification is carried out on behalf of the TETRA Association by ISCOM – the independent laboratory of the Italian Ministry of Communications.
During Spring 2007, EADS undertook the ISI interoperability test session. Each TIP test case was analysed by ISCOM from logs and test equipment. It was not just a demonstration but also a verification of all specifications, test plans and processes.
EADS proved that the ISI protocol works and can interface systems in the standardised way. From now on, any country may benefit from TETRA with ISI by interfacing several regional TETRA systems from different suppliers, provided that these systems correspond to the ISI protocol as defined in TETRA standard.
TETRA ISI unique user benefits:
1. Interconnection of the networks can be practically invisible to the radio users, with networks from different manufacturers interconnected in a standard manner.
2. Radio users will receive their calls regardless of their location. The mobility management in TETRA ISI keeps track of the users’ location, ensuring the calls are routed correctly.
3. TETRA ISI defines a wide range of voice services. In addition to group calls, there can be one-to-one calls; priorities of calls and callers range from low to extremely high; end-to-end encryption, and the caller’s identity shown or restricted.
4. Users have all data services at hand. The short data service defined in TETRA ISI means that the same operational status and text messages are available for the user, also when operating in another TETRA network. The packet data interconnection is also available.
5. Professionals do not have to compromise security of communications.
6. TETRA ISI gives network owners and operators the choice of multiple providers for their networks.
TETRA ISI timeline:
2000 and 2001 – TETRA community workshops defined clear operational user requirements and prioritised them. In addition, it was agreed to implement the ISI in several phases.
2002 – The first set of TETRA Interoperability Profile (TIP) specifications for ISI was published. These specifications define, in effect, how everything is supposed to work, so this was also the time when manufacturers could start their implementation work.
2001 to 2003 – The Three Country Pilot took place in the border areas of Belgium, Germany and the Netherlands. The pilot simulated cross-border field operations and provided valuable input for the development of ISI.
2005 – EADS’s TETRA network was certified to meet the pre-ISI requirements. In practice, this meant that a radio user was able to move from one network to another in a standardised way.
2007 – All necessary specifications, test plans and processes were in place and ISI certification could start.
June 2007 – The world’s first TETRA ISI interoperability certificate was awarded to EADS.
TETRA ISI available today:
Purchasers of TETRA networks today can now specify cross-network connectivity that adheres to the TETRA standard. Interconnecting TETRA networks by different vendors is no longer necessary through a collection of analogue and PABX interfaces, nor is it necessary to sacrifice services.
This year has proven that the TETRA ISI can be implemented. It has proven that the specifications are clear. Above all, TETRA ISI exists – it is now a delivered promise.
TETRA News 2007 Edition No2 (September 2007)